HELSINKI, SEPT. 9 -- By insisting today on a complete Iraqi withdrawal from Kuwait, President Bush and Soviet President Mikhail Gorbachev were not only advancing a new era in superpower cooperation, but also putting the combined international prestige of their two countries on the line.

The first U.S.-Soviet attempt at joint crisis management since the end of the Cold War achieved what Gorbachev described, with a touch of hyperbole, as "a kind of solidarity that has never been expressed before in the history of the world." But it remains to be seen what kind of impression this will produce on Iraq's Saddam Hussein.

Will the Iraqi ruler see the unprecedented U.S.-Soviet cooperation as affirmation that he really is, as Gorbachev said today, "driving into a dead end?" Or will Saddam zero in on the clear differences between Bush, who is open to the use of military force, and Gorbachev, who is not, and see the Soviet refusal to go along with military action at this stage as a brake on Bush's ability to act?

Also unresolved was the question of what to do about Saddam if the economic blockade and diplomatic pressures fail.

Despite Gorbachev's hopes that the Iraqi leader will "display sobriety" and respond to the global appeal to get out of Kuwait, both Bush and Gorbachev seem to be preparing for the long haul.

The U.S. president persuaded the Soviet leader to consider the possibility of new action by the United Nations against Baghdad if economic sanctions fail to produce the desired result.

But Bush also tacitly committed himself to exhausting all diplomatic options before resorting to force. The result of the meeting seems to suggest that a possibly long period of waiting in the desert may lie ahead for U.S. and Arab forces as the superpowers wait to see if either diplomacy or the U.N.-mandated sanctions on Iraq have any affect on Saddam.

The unprecedented unity of purpose between the two superpowers is likely to increase the psychological pressure on Saddam to search for a face-saving way out of a crisis of his own making, Soviet officials here said. They are convinced, they said, that their former protege is a rational politician who would be prepared to make a deal.

But the minimum demands of Washington and Moscow may be more than Saddam can swallow without jeopardizing his hold on power in Baghdad.

The Iraqi leader recently surrendered all of his gains in his 1980-88 war with Iran to concentrate his military resources on the gulf crisis, and if he now gives up Kuwait, some analysts say he could be toppled from within.

As Gorbachev and Bush gave their joint press conference here this evening, exchanging affectionate gestures like old friends, their political need for one another was quite apparent.

Bush needs Gorbachev because the Soviet Union, for all its diminished superpower status and appalling domestic problems, still possesses a U.N. Security Council veto as well as the ability to cause international mischief. Without Soviet backing, Bush would be less able to claim that the contest in the Persian Gulf is between the international community and Saddam Hussein.

Gorbachev needs Bush for different but equally compelling reasons. He needs an infusion of Western assistance for his country's devastated economy, which will be much easier to get if he has Washington's official "Good Housekeeping" seal of approval. He wants to maintain his own image as the international statesman who consigned the Cold War to the garbage dump of history. And he also is anxious to show that the Soviet Union still matters in world affairs.

"In today's world, no single country, however powerful, is able to provide the leadership which individual countries tried to provide in the past, including some countries that are represented here. We can only succeed if we work together," said Gorbachev, effectively acknowledging Soviet weakness, but also raising questions about the ability of the United States to impose its will on the rest of the world.

Gorbachev was clearly stung by Saddam's charge, made in an internationally televised broadcast last night, that Moscow's support for Washington's handling of the gulf crisis was a reflection of the Soviet Union's decline as a world power.

Gorbachev accused Saddam of leading Iraq into a "dead end" by cutting it off from the international community. The Kremlin, he said, would continue to cooperate with other members of the Security Council.

The real significance of today's meeting for the Soviets was that it confirmed that after seven decades of international isolation, they have finally come in from the cold. First lady Barbara Bush went so far as to remark informally to reporters that the Soviet Union should now be considered "part of the Free World."

Bush seemed anxious to reward Moscow for its new, cooperative mood. He gave his most positive assessment yet of the prospects for economic cooperation between the superpowers, saying he would be addressing Congress on this matter after his return to Washington.

Gorbachev's press spokesman, Vitaly Ignatienko, later told reporters that the two leaders had discussed a number of joint economic projects. Gorbachev, however, was sensitive at the press conference to Bush's linkage of U.S. economic assistance for Moscow to a strong Kremlin stand against Iraq. "It would be very oversimplified and very superficial to judge that the Soviet Union could be bought for dollars," the Soviet leader replied.

On the diplomatic front, Bush conceded a point that has been on the Kremlin's political wish list for more than three decades: recognition that the Soviet Union has a legitimate role to play in the Middle East.

The joint statement acknowledges that both superpowers should work actively together to "resolve all remaining conflicts" in the region as soon as the Kuwaiti crisis has been resolved. In Gorbachev's interpretation, this means the end of a long-standing U.S. attempt to cut Moscow out of negotiations for a settlement of the Arab-Israeli dispute.

After attracting everybody's attention by saying he was about to reveal "a secret," Gorbachev quoted Bush as telling him that there had been a long period when the United States felt that the Soviet Union had "no business" in the Middle East.

"This was something that we had to talk through during this meeting here in Helsinki. And what was said here is that it's very important for us to cooperate in the Middle East, just as on other issues of world politics," he said.

In return for these symbolic concessions by Washington, Gorbachev did not go substantively beyond his previous position on the crisis. He turned down a request by Bush for the immediate withdrawal of Soviet military specialists from Iraq, saying only that their numbers are now down from nearly 200 to around 150. And he continued to insist on a political solution to the crisis, while acknowledging that a "provocation" by Saddam could plunge the region into a "tragic" war.

Gorbachev's ambiguous stand over the military advisers is a reminder that the Kremlin is unwilling to burn its bridges with Saddam entirely. To pull the advisers out precipitously could provoke retaliation by Baghdad against the remaining 6,000 or so Soviet citizens in the country.

Equally important, it would be a signal to the radicals in the Arab world that the Soviet Union has ceased to care about relationships built up over many years for the sake of its new-found friendship with the United States.

Unlike Bush, who is opposed to any "linkage" between the Kuwaiti crisis and other Middle East problems, Gorbachev made clear that he wants swift action on the Arab-Israeli dispute.

"Failure to find a solution in the Middle East at large also has a bearing on the acuteness of the particular conflict we've been talking about here," the Soviet president said, in a token gesture toward Saddam. The Iraqi leader has offered to consider withdrawing from Kuwait if Israel leaves the territories it occupied in the 1967 Arab-Israeli War and if Syria pulls its troops out of Lebanon.

Like previous superpower meetings, the Helsinki summit has provided Gorbachev with a respite from his growing domestic problems. But as he returns home, both he and his entourage are well aware that his successes on the international stage could be overwhelmed by failure at home.

With Soviet citizens now facing the indignity of lining up for bread for the first time in more than 30 years, Gorbachev this week will make yet another attempt to sell an economic reform plan to the increasingly skeptical Soviet populace.

"This summit provides further confirmation of Gorbachev's standing in world affairs," said Stanislav Kondrashev, a leading commentator for the Soviet government newspaper Izvestia. "But the domestic political benefits from this kind of meeting are steadily diminishing. Unlike Americans, for whom the gulf crisis overwhelms everything else, Soviets are preoccupied by economic problems."